1. Field of the Invention
The present invention relates to magnets having a field-shaping mechanism. More particularly, it relates to apparatus and methods for reshaping magnetic fields by bending, straightening or otherwise flexing flux lines from their original position.
2. Description of the Prior Art
The use of magnetic claddings and cores to shape or concentrate the magnetic field of a magnet is known. Such claddings are often used to produce a magnetic field having a desired configuration. For example, tubular solenoids are often clad with cylindrical metal cases for improved magnetic circuit return as well as coil protection. These dc solenoids offer high volumetric efficiency and, as such, they are often specified for industrial and military/aerospace equipment where space is at a premium. They are used in printers, computer disks and tape drives, and military weapons systems. Those concerned with the development of such solenoids have routinely used claddings made of metal such as iron to shape and direct the solenoid fields so as to closely approximate the field of an ideal solenoid.
The ideal solenoid is often viewed as an infinitely long, current-carrying wire wound in the form of a close-packed helix. Essentially, the ideal solenoid is an infinitely long conductive cylinder in which a sheet of current flows that produces a uniform magnetic field having induction lines that are parallel for all points inside the cylinder and wherein the field is essentially zero for all points outside the cylinder, the field lines closing on themselves at infinity.
In many applications, solenoids of finite length are good approximations of the ideal solenoid for points close to the solenoid axis and for external points near the central region of the solenoid, that is, away from the ends. The approximation becomes better for a solenoid wherein its length is much greater than its diameter. However, in many applications, increasing the length of a solenoid becomes impractical. It is for this reason that those skilled in these arts have often used magnetic claddings, cores, and other means to help direct the solenoid field into a near uniform configuration more like the ideal case. Although, such prior art devices have served the purpose, they have not proved entirely satisfactory under all conditions of service for the reason that the added bulk and weight of claddings and similar devices make their use impractical in many applications. Additionally, claddings and cores can provide only a limited degree of field shaping.